SECRET OF THE OBELISKS
In this adventure, we learn the secret of the obelisks that have appeared in other fifth edition adventures published by Wizards of the Coast, including Tomb of Annihilation and Waterdeep: Dungeon of the Mad Mage.
The first group of these magical obelisks was crafted by a secret society of spellcasters called the Weavers. These obelisks could alter reality on a grand scale, sending a region or an entire world back to an earlier time (effectively erasing part of history). The obelisks were constructed to counteract the effects of calamitous spells and cataclysmic events.
An evil wizard named Vecna stole one such obelisk and used it to erase the obelisk’s creators from existence. Vecna also stole the knowledge needed to create new ones. That knowledge later came into the possession of Netherese wizards, who built similar obelisks of their own. They believed that if some catastrophe destroyed their empire, these obelisks could help restore it. Unfortunately for them, most of the obelisks built to protect Netheril were stolen or otherwise lost over time, as were records of their purpose and information about how to activate them.